1. Field of the Invention
The present invention relates to a heat exchanger plate for an evaporator and an evaporator with a plurality of heat exchanger plates which are stacked above one another, especially for a drive train of a motor vehicle, rail vehicle or a ship for example, comprising an internal combustion engine and a steam motor, with the heat of a hot medium such as a hot exhaust air flow, hot charge air, coolant, cooling agent or an oil of the internal combustion engine or a further unit provided in the drive train such as a vehicle air-conditioning system being used in the evaporator for generating the steam for the steam motor. The present invention is not limited to the application in a mobile drive train, but stationary drive trains such as in industrial applications or block-type thermal power stations can also be arranged accordingly.
2. Description of the Related Art
Heat exchanger plates or evaporators for utilizing the waste heat in a drive train, especially a drive train for a motor vehicle with an internal combustion engine, to which the present invention relates according to one embodiment, have long been known. The heat contained in an exhaust gas flow of the internal combustion engine is used for evaporating and/or superheating a working medium, and the vaporous working medium is then expanded in an expansion machine, i.e. a piston engine, turbine or screw machine, under release of mechanical power and is thereafter supplied to the evaporator again. The working medium is condensed after the expansion machine and then supplied to the evaporator again.
The utilization of the exhaust gas heat of the recirculated exhaust gas flow of modern diesel engines is especially advantageous, but also of petrol engines because in this case the offered heat is available at a high temperature level. At the same time, the cooling system of the vehicle is relieved because the heat flow of the recirculated exhaust gas is decoupled from the cooling system and is used in the evaporation circuit process for generating useful power. It is simultaneously or alternatively advantageous to use the residual exhaust gas flow for preheating, evaporation and/or superheating a working medium, which until now flowed out of the rear muffler to the ambient environment in an unused manner.
A further heat source which can be used at least for preheating, partial evaporation or even complete evaporation of the working medium in such a drive train is the heat contained in the coolant of a cooling circuit of the motor vehicle or the internal combustion engine. Further heat sources are obtained by exhaust gas recirculation and charge air cooling of vehicle engines and intermediate cooling in multi-step charging of the internal combustion engine. A separate burner unit can also be provided additionally or alternatively, or the heat of other heat sources in the drive train, especially the vehicle drive train, can be used such as engine oil, gear oil or hydraulic oil and electronic components, electric motors, generators or batteries that are provided there.
The mechanical power generated in the expansion machine from waste heat can be utilized in the drive train, either for driving auxiliary units or an electric generator. It is also possible to use the drive power directly for driving the motor vehicle, which means for traction, in order to thereby provide the internal combustion engine with a more compact size, to reduce fuel consumption or provide more drive power.
Various requirements are placed on the heat exchanger plates or the evaporators in the mentioned fields of application. On the one hand, they should offer high efficiency and work reliably. On the other hand, they should be produced at low cost and have a low overall volume and a low weight. Finally, the problem arises during use in the exhaust gas flow of an internal combustion engine that the volume flow of the exhaust gas will vary extremely during operation of the internal combustion engine and is further subject to temperature fluctuations. The exchanger plate or evaporator must be capable of securely managing such fluctuations in volume flow and temperature and securely ensuring the desired evaporation of the working medium in any possible state.
Document U.S. Pat. No. 4,665,975 A describes a plate heat exchanger, in which relatively large channels are provided which extend in the direction of the transverse axis for transverse distribution of the flow. Meandering channels which are switched in parallel and are tightly separated from one another are provided in the direction of flow before the comparatively large channels which extend in the direction of the transverse axis.
Further plate heat exchangers and methods for their production are disclosed in the publications DE 10 2006 013 503 A1, DE 30 28 304 A1.
Document EP 1 956 330 A2 describes a heat exchanger with a transverse flow distribution device for the fluid to be evaporated, in which the fluid to be evaporated flows laterally into the transverse flow distribution device in the direction of the transverse axis and is then redirected in the direction of the longitudinal axis in individual channels connected with one another via boreholes.
Document U.S. Pat. No. 3,983,191 A describes the lateral introduction of a fluid into a plate heat exchanger, in which the fluid flows at the top over a perforated rib in the direction of the transverse axis, whereas the steam is able to flow over the entire width of the rib through the same.
U.S. Pat. No. 4,249,595 describes the distribution of steam flowing from below into the heat exchanger via a strip with a plurality of nozzles. This injection via nozzles prevents that the fluid flowing from the top to the bottom is able to flow over the strip and will reach the flow distribution area for the steam.
The present invention is based on the object of providing a heat exchanger plate or an evaporator with a plurality of such heat exchanger plates which fulfills the mentioned requirements optimally.